1. Field of the Invention
The present invention relates to a negative resist composition, a patterning process, and a testing process and a preparation process of the negative resist composition.
2. Description of the Related Art
It is well known that, as LSI progresses toward a high integration and a further acceleration in speed, miniaturization of a pattern rule is required. With this move, an exposure method and a resist composition are changing significantly; especially when a lithography of the pattern with 0.2 μm or less is performed, the light sources such as an excimer laser of KrF and ArF, an electron beam, and the like are used, while a chemically amplified type having a good sensitivity to such high energy beams and giving a high resolution is used for a photo resist.
In a resist composition, there are a positive type in which an exposed part is dissolved and a negative type in which an exposed part remains as a pattern. They are selected based on the ease of its use and depending on the required resist pattern. A chemically amplified negative resist composition usually contains a polymer soluble in an aqueous alkaline developer, an acid generator generating an acid by decomposition with an exposure light, a crosslinker that insolubilizes the polymer into a developer by crosslinking the polymers among themselves by action of the acid as a catalyst (in a certain case a polymer and a crosslinker are integrated together), and, in addition, usually a basic compound to control diffusion of the acid generated by the light exposure.
Many negative resist compositions using the unit having a phenolic hydroxyl group as the alkaline-soluble unit in a polymer that is soluble in the aqueous alkaline developer have been developed, especially for exposure to a KrF excimer laser beam. These have not been used for an ArF excimer laser beam because the phenolic unit does not transmit the light when the exposure light having the wavelength of 150 to 220 nm is used. However, in recent years, these have been drawing attention again as the negative resist composition for exposure to EB and EUV, which are exposure methods to obtain a further finer pattern, as reported in Japanese Patent Laid-Open (kokai) No. 2006-201532, Japanese Patent Laid-Open (kokai) No. 2006-215180, and Japanese Patent Laid-Open (kokai) No. 2008-249762.
In order to perform fine processing as required in the EB and the EUV exposures as mentioned above, the resist film inevitably needs to be made thinner. This is because it is impossible to avoid the problem such as pattern delamination during development when the ratio of the pattern height to the pattern line width, the so-called aspect ratio, is too large. On the other hand, when the resist film is made thin, there appears the problem whether or not a satisfactory etching selectivity can be obtained at the time of transformation of the resist pattern to the film to be processed by using the resist pattern obtained from the said resist film. To address this etching resistance problem, a multi-layer resist method, in the case of processing of a semiconductor device (for example, Japanese Patent Laid-Open (kokai) No. 2008-96684) and an etching mask film method, in the case of processing of a photomask (for example, Japanese Patent Laid-Open (kokai) No. 2007-241060), have been proposed. As a result, a method, with which the etching contrast can be obtained even when a thin resist film like the one having the film thickness of 100 nm or less is used, is becoming available.
In the lithography by a resist film having the thickness of 100 nm or less as mentioned above, a part of the problem in etching resistance has been solved by the use of an etching auxiliary film and the like. However, it became clear that the requirement cannot be necessarily satisfied by the method in which the resist film is merely made thinner in order to obtain both of the etching resistance of the resist film to be used and the high resolution simultaneously.